In reply to lamb:
I've got a lovely Merino one, which is great, and a cheapo berghaus x-static one , which is also very good, and I have a paramo reversible one (one side is supposedly cooler than the other), whish is really good too. So Id' recommend the previous three brands, but I'm not a big helly hansen, lowe alpine, or north face fan for base layers.
If you can afford it then get merino.
Josh.